An internal combustion engine demonstrating one or more of inverse displacement, asymmetrical cycles, and continuous torque generation is described.
An internal combustion engine is a heat engine in which the thermal energy comes from a chemical reaction within the working fluid. The working fluid in an internal combustible engine is fuel, such as gasoline, diesel fuel, and the like, as known to practitioners in the art, and air. Heat is released by a chemical reaction of the fuel and rejected by exhausting spent fuel by-products into the environment. In contrast, in an external combustion engine, such as a steam engine, heat is transferred to the working fluid through a solid wall and rejected to the environment through another solid wall.
Internal combustion engines have two intrinsic advantages over other engine types such as steam engines. First, they require no heat exchangers except for auxiliary cooling, reducing the weight, volume, cost and complexity of the engine. Secondly, internal combustion engines do not require high temperature heat transfer through walls. Thus, the maximum temperature of the working fluid can exceed the maximum allowable wall material temperature. However, internal combustion engines also have known intrinsic disadvantages. In practice, working fluids can be limited to a combustible source, air, and products of combustion, and there is little flexibility in combustion conditions. Non-fuel heat sources such as waste heat, solar energy and nuclear power cannot be used. Further, internal combustion engines, as currently designed, can be very inefficient.
However, the advantages far outweigh the disadvantages of using an internal combustion engine. The four-cycle internal combustion engine based on the Otto cycle has widespread use in society today. More internal combustion engines are in use than all other types of heat engines combined. One problem with the internal combustion engine is poor engine efficiency. Current technology available for internal combustion engine design results in efficiencies of about 25% in converting the energy of the working fluid to usable power. Thus, poor engine efficiency increases the need for fuel while at the same time contributing high levels of pollutants to the atmosphere.
Engines are designed to convert fuel to usable power. In an internal combustion engine, the fuel is burned to provide force in the form of high pressure, which can be translated by some mechanical means into torque, or rotational movement, to move a desired object, such as an automobile driveshaft, saw blade, lawn mower blade, and the like. The torque about an axis of rotation at any given time, as described by Archimedes Principle, is equal to the product of the perpendicular force vector times the distance from the axis of rotation that the force is applied. Horsepower is related to torque output of an engine by the formula:
Horsepower=Torque*(Revolutions per Minute/5252)xe2x80x83xe2x80x83(1)
Torque is limited in current engine designs by the amount of force that can be applied to the crank shaft at any given time, and the geometry of the mechanical translation that controls the angle and distance from the crank shaft at which the force is applied. In current internal combustion engine technology, there is little flexibility to change the geometry of the mechanical translation of force into torque. In order to increase torque, an increase in the amount of force generated is required, which would create a larger displacement engine and require more fuel.
A focal point in current internal combustion engine technology is the relationship between horsepower (hp) output and cubic inch of engine displacement, or total engine working volume. A desirable relationship between horsepower and cubic inch of engine displacement is approximately 1 to 1. This means that 1 hp of output is generated for each cubic inch of engine displacement. However, most internal combustion engines currently available do not have this 1:1 relationship, achieving only about 0.85 hp per cubic inch of engine displacement. With various known incremental improvements in design, for example, the addition of a turbo charger, horsepower output levels can be increased beyond about 1 hp per cubic inch of total engine displacement. Current improvements to efficiency are, however, only incremental in benefit and at a cost of great complexity and expense.
Most internal combustion engines are piston engines. In an internal combustion piston engine, fuel can be burned to create pressure, which can be used to create force for movement of the piston. As shown in FIGS. 1a-1d, in a piston engine, fuel can be directed into a chamber and compressed by a piston. A spark can be used to ignite the fuel, causing combustion of the fuel and an increase in the pressure and temperature inside the chamber, which causes an expansion of the working volume in which the fuel can be located. The combustion products, or exhaust, can be released to the environment. This sequence of four cycles, known as (1) intake, (2) compression, (3) combustion and (4) exhaust, are known collectively as an Otto cycle. Almost all internal combustion engines today can be designed using the Otto cycle. The sequence of the Otto cycle occurs in the order listed. The compression and combustion cycle are companion cycles. Most of the work input occurs during the compression cycle, while most of the output power can be generated during the combustion cycle. These two cycles are reverse processes of each other and are typically shown graphed together with like coordinates on a pressure volume (PV) diagram, which shows the net work output of the system. The exhaust and intake cycles are also companion cycles, and are reverse processes of each other in traditional engines. During the exhaust cycle, the working volume can be reduced to expel exhaust, and during the intake cycle, the working volume can be expanded to intake fuel. The exhaust and intake cycles are not graphed on a PV diagram because the work done during each cycle can be considered negligible. An exemplary PV diagram is shown in FIG. 2, and illustrates the compression cycle between A and B, the ignition of the fuel and increase in pressure in the working volume between B and C, the combustion cycle and expansion of the working volume between C and D, and the exhaust and intake cycles between D and A.
Compression and combustion are reverse processes of each other, and exhaust and intake are also reverse processes of each other, in that the way the working volume contracts during combustion or exhaust is the exact reverse process of the way it expands during combustion or intake, respectively. The total change in the working volume during each movement of a piston can be the same but in the opposite direction of the change in working volume of the previous movement of the piston, and the direction of piston movement can be the same but in the opposite direction of the previous movement. The mechanical translation of piston force into torque and torque back into force on the piston are reverse mechanical processes.
As shown in FIGS. 1a-1d, each individual stroke of a piston engine corresponds to a linear movement of the piston 20 within a chamber 10. As the piston 20 moves along the chamber wall in a direction 26 as shown in FIG. 1a, creating an increase in the working volume 170, fuel can be brought into the chamber 10 from the intake port 60, forming the intake cycle (FIG. 1b). At the end of the intake cycle and as shown in FIG. 1c, the piston 20 reverses direction of movement along the chamber wall, moving in direction 27, and compressing the fuel and present air as shown in FIG. 1d, forming the compression cycle. Near the beginning of the combustion cycle (FIG. 1a), the compressed fuel/air mixture can be ignited by a spark from the ignition port 80, causing the fuel/air mixture to dramatically increase in temperature and pressure, igniting and burning the fuel to create gasses. The trapped gasses cause an increase in pressure in the working volume, causing the working volume 170 in the chamber to expand (FIG. 1b). The energy of the contained combustion creates force that can be used to create torque. The combustion products can be exhausted to the external environment through an exhaust port 70 during the exhaust cycle (FIG. 1d). A piston traverses the length of a chamber four times in order to move through the sequence of the Otto cycle, as illustrated above. A piston can move through the Otto cycle sequentially. However, because work is extracted only during the combustion cycle, more than one piston can be used and interconnected such that at least one piston can be generating torque at any given time, pushing the other pistons through the other cycles. Even multiples of pistons, such as 2, 4, 6, 8, or more can be used in conjunction, one or more pistons being in a different portion of the Otto cycle than the remaining pistons at any given time. The movement of multiple pistons in opposite directions provides a balanced movement so the engine does not vibrate uncontrollably, and can make the engine easier to start.
In the piston engine as shown in FIGS. 1a-d, the movement of the piston 20 in the chamber 10 can be translated into torque by connection of the piston 20 to a crank shaft 50 through a connecting rod 30 and crank arm 40, connected to connecting rod 30 by crank pivot 42. The motion 26, 27 of the piston 20 can be in line with the crank shaft 50. The crank shaft turns in a circular motion 28, driven by the force of the linear movement of the piston. Torque is equal to force times the perpendicular distance the force is applied from the pivot point, in this case, the crank shaft 50. At the beginning of the combustion cycle, the piston 20 and crank arm 40 can be in alignment with the crank shaft 50 and the entire force of the piston 20 can be directly on top of the crank shaft 50, as shown in FIG. 1a. The perpendicular distance the force is applied to the pivot point at that instant is zero, and the torque generated is zero. It is not until the crank shaft 50 rotates some amount that the crank arm 40 will gain some perpendicular distance from the crank shaft 50 and start to generate torque. This relationship varies approximately as the sine of the angle A that the crank arm 40 makes with the line of piston motion. The force on the piston 20 can be largest near the beginning of the combustion cycle when the fuel first combusts and is under maximum pressure and minimum volume. This massive component of energy is lost because the mechanics of the engine don""t allow the force from the piston to be applied in the direction that will generate torque, that is, at an angle to the crank shaft. In effect, the force from the piston is only partially translated into torque, with the rest of the force being dissipated as waste heat. A large component of energy loss in current internal combustion piston engine technology occurs because of the mechanical limitations of converting the force from the piston into torque on the shaft. This issue is also present in current internal combustion rotary engine technology, such as a xe2x80x9cWankelxe2x80x9d rotary engine, as shown in FIGS. 3a-c. 
In its most basic form and as shown, for example, in FIGS. 3a-c, a rotary engine typically has a single symmetrical chamber 10. In place of a piston is a multi-face rotor 22 that pushes against a chamber wall as it rotates within the chamber 10 around a crank shaft 50. The rotor can rotate clockwise, for example, as shown in FIGS. 3a-c. As the rotor 22 turns, it creates changes in the working volumes 170a, 170b, and 170c, necessary for each of the four cycles of the Otto cycle to occur. For a Wankel rotary engine, the chamber 10 can be approximately oval with the crank shaft 50 at the center. The rotor 22 for a Wankel rotary engine has a roughly triangular shape, forming three convex shaped rotor faces 5a-c and three separate working volumes 170a-c. A circular hole 55 for the crank shaft 50 can be set in the center of the rotor 22. The rotor 22 makes a symmetrical motion around the crank shaft 50. The shape of the chamber wall can be designed such that all three apices 21a-c of the rotor 22 can be in constant contact with the chamber wall as the rotor 22 turns around the crank shaft 50 to complete each of the four cycles, as demonstrated in FIGS. 3a-c. The inside of the rotor 22 interacts with and turns the crank shaft 50 by means of a gear (not shown) located on the inside of the circular hole 55. As in the piston engine, an intake port 60, exhaust port 70, and ignition port 80 can be present in order to provide fuel to, expel fuel from, and ignite fuel in the working volume 170a-c, enabling the Otto cycle.
In a rotary engine, there is little flexibility in changing the shape of the chamber wall or rotor. Torque can be generated by the interaction of the rotor face and the chamber wall. As in the piston engine, the problem of zero torque generation during some portion of the combustion cycle is present. When the rotor face and chamber wall push directly against each other with no angle of incidence between them, which can be the case at both the beginning and end of the combustion cycle, no torque is generated. The rotor face must push against the chamber wall at some angle of incidence in order to slide along the chamber wall, spinning the shaft and generating some component of torque. In a rotary engine, the direction the rotor and chamber wall push against each other is in alignment with the shaft at the beginning of the combustion cycle, and at the end of the combustion cycle. Thus, just as in the piston engine, the torque generated by the rotary engine is zero at both the beginning and end of the combustion cycle, wasting much of the generated force. It is noted that in a rotary engine, the torque varies as a function of the angle of incidence between the direction of force generated by the rotor face and the direction of the force from the outside chamber wall, and is equal to the force from the rotor face times the sine of the angle of incidence times the cosine of the angle of incidence. The angle of incidence varies from about 0 degrees to about 20 degrees. This can result in less mechanical translation of force into torque than is present in a piston engine, wherein torque varies as a function of the sine of an angle that ranges from 0 to 180 degrees.
Traditional internal combustion engines translate some of the force on the piston or rotor into torque about the crank shaft. In looking at a geometrical relation of the piston and crank shaft, a mathematical expression for the calculation of torque for a piston engine can be written. FIG. 4 depicts the geometric relation of the piston force F(p), connecting rod L, crank arm C and crank shaft CS from which a mathematical expression can be derived. As shown in FIG. 4, as the crank arm C rotates around the crank shaft, angle A can be created. At the beginning of the combustion cycle, angle A is equal to zero degrees. Angle A increases to 180 degrees as the combustion cycle progresses. The torque around the crank shaft at any time during the combustion cycle can be calculated by summing the horizontal and vertical components of torque, F(x) and F(y), created by the movement of the connecting rod L and the crank arm C, using known trigonometric and algebraic substitutions, as follows:
Torque=F(x)*C*sin(A)+F(y)*C*cos(A)xe2x80x83xe2x80x83(2)
L{circumflex over ( )}2=X{circumflex over ( )}2+Y{circumflex over ( )}2xe2x80x83xe2x80x83(3)
Y=C*sin(A)xe2x80x83xe2x80x83(4)
Substituting to solve for X in formula (3) yields:
X={square root over (L{circumflex over ( )})}2xe2x88x92C{circumflex over ( )}2*(sin(A)){circumflex over ( )}2xe2x80x83xe2x80x83(5)
F(y)/F(x)=Y/X=C*sin(A)/{square root over (L{circumflex over ( )})}2xe2x88x92C{circumflex over ( )}2*(sin(A)){circumflex over ( )}2xe2x80x83xe2x80x83(6)
Presuming F(x)=F(p):
F(y)=F(p)*C*sin(A)/{square root over (L{circumflex over ( )})}2xe2x88x92C{circumflex over ( )}2*(sin(A)){circumflex over ( )}2xe2x80x83xe2x80x83(7)
Substituting the above into formula (1) yields:
Torque=F(p)*(C*sin(A)+C{circumflex over ( )}2*cos(A)*sin(A)/{square root over (L{circumflex over ( )})}2xe2x88x92C{circumflex over ( )}2*(sin(A)){circumflex over ( )}2)xe2x80x83xe2x80x83(8)
As shown in equation (2), the total torque in an engine can be equal to the force F(x) times its perpendicular distance from the shaft, which is C*sin(A), plus the force F(y) times its perpendicular distance from the shaft, which is C*cos(A). Substituting the relationships between F(x), F(y), and F(p) yields equation (8) for torque. Because the equation for torque has a sin(A) in each component, torque will vary as sin(A). Torque is equal to zero when A is zero degrees or 180 degrees. The mechanical translation function of force into torque for a 1 liter piston engine is shown graphically in FIG. 5 as line P.
In a piston engine, force on the piston is largest near the beginning of the combustion cycle when the pressure inside the chamber is the largest. At the beginning of the combustion cycle, angle A is zero degrees, and the components of torque are equal to zero. The entire force from the piston near the beginning of the combustion cycle is dissipated as heat and friction because it is not translated into torque, wasting energy. Torque does not begin to be generated in a traditional piston engine until the crank arm rotates some amount beyond zero degrees.
Traditional rotary engines generate torque in a different way than piston engines. Rotary engines generate torque by two surfaces interacting or pushing at an angle against each other. The torque is a function of the angle of incidence between the direction of the forces generated by the rotor face and stationary concave chamber wall surface. When the forces of the two surfaces push in exact opposite directions, no component of torque can be generated because the force of the rotor F(r) and the force of the wall F(s) are in line with the crank shaft CS, generating no angle of incidence, as shown in FIG. 6. In order for a component of torque to be generated, the forces have to push against one another at some angle of incidence greater than 0 degrees and less than 90 degrees. Intersection of the forces generated at some angle other than 0 degrees or 90 degrees will cause sideways movement of the interacting surfaces in relation to each other about the crank shaft CS and generation of a component of torque F(t), as shown in FIG. 7. As shown in FIG. 7, torque can be equal to the force of the rotor F(r) times the distance D from the crank shaft CS to the chamber wall S, times cos(C)*sin(C), where C is the angle of incidence formed between the chamber wall and the direction of the component of force generating torque F(t), and F(s) is the force of the chamber wall.
Torque=F(t)*Dxe2x80x83xe2x80x83(9)
Component of force along the chamber wall=F(s)*sin(C)xe2x80x83xe2x80x83(10)
Component of force generating torque F(t)=F(s)*sin(C)*cos(C)xe2x80x83xe2x80x83(11)
F(s)=F(r), wherein F(r)=force from the rotorxe2x80x83xe2x80x83(12)
Torque=F(r)*sin(C)*cos(C)*Dxe2x80x83xe2x80x83(13)
The value of sin(C)*cos(C) has a maximum value at 45 degrees. At 45 degrees, the value of cos(C)*sin(C) is equal to xc2xd.
The traditional rotary engine has a similar problem in the mechanical translation of force into torque as is present in the traditional piston engine. In the rotary engine, the direction of force from the rotor face and the direction of force from the outer chamber wall can be in alignment at the beginning and end of the combustion cycle. No torque can be generated at the beginning and end of the combustion cycle because the forces of the rotor face and outer chamber wall are aligned with each other, and are each aligned with the crank shaft, creating no angle of incidence. It is only during the middle portion of the combustion cycle that the rotor face and outer chamber wall are pushing against each other at an angle greater than 0 degrees and less than 90 degrees to create a component of torque.
A further problem in achieving a greater translation of force into torque with current technology can be the length of the crank arm. Torque equals the force times the perpendicular distance away from the pivot point or crank shaft that the force is applied. If the crank arm were made longer, more torque would be generated than with a shorter crank arm because there would be more distance between the crank shaft and force point. Functionally, the length of the crank arm is limited by the mechanics of the engine, for example, by the compression ratio of the fuel in the engine. A longer crank arm would correspond to a higher compression ratio during the compression cycle. In the case of a piston engine, the piston would need to travel a longer distance. However, a longer travel distance of the piston means a larger total engine displacement and a higher compression ratio for the fuel and air mixture during the compression cycle. Compression ratios for gasoline, the most common fuel source, are limited to a maximum of about 10:1 before the gasoline detonates. The crank arm length in an engine is determined by the mechanics of the engine and the maximum compression ratio of the fuel. The crank arm length can not be increased because this would result in a higher compression ratio than the maximum compression point of the fuel source.
As described herein and known in the art, torque in an engine translates into horsepower by the Formula (1). More horsepower can be generated if the mechanical translation means to convert existing force on a piston or rotor into torque continuously throughout the combustion cycle can be determined while maintaining favorable thermodynamic and fluid mechanic properties. Greater torque, and therefore horsepower, can be generated if the mechanical means can be determined that can apply force at a more favorable distance from the shaft during the combustion cycle.
According to various embodiments, an internal combustion engine which achieves greater torque as compared to a traditional internal combustion engine is described. According to various embodiments, an internal combustion engine capable of generating a relationship of horsepower per cubic inch of displacement of about 4 to 1 is described.
According to various embodiments, a rotary engine having a concave-shaped contour moving about a fixed convex contour is described.
According to various embodiments, an internal combustion rotary engine capable of generating torque continuously throughout the combustion cycle is described. According to various embodiments, torque can be generated continuously throughout the entire combustion cycle by controlling the angle of incidence of the force generated by a concave-shaped contour and the opposing force generated by a stationary surface.
According to various embodiments, a crank arm length of an internal combustion rotary engine as described herein can be longer than a crank arm length of an internal combustion piston engine of the same displacement.
According to various embodiments, an internal combustion engine has at least two concave-shaped contours and one shaft located within each of at least two chambers set at 180 degrees to each other, forming a balanced engine assembly. According to various embodiments, each chamber can be asymmetrically shaped.
According to various embodiments, an internal combustion engine having a crank arm that varies in length throughout the engine cycle is described. According to various embodiments, the crank arm length can increase during the combustion cycle and decrease during the compression cycle.
According to various embodiments, a crank shaft can be located off-center within a chamber of an internal combustion rotary engine.
According to various embodiments, an internal combustion engine can have cycles of combustion, compression, intake and exhaust which are asymmetric with respect to changes in a working volume.
According to various embodiments, an internal combustion engine can have asymmetric translation of force into torque between the cycle of combustion and the cycle of compression.
A method of generating continuous torque during a combustion cycle is described